So I've decided I really want an mtr4b...... but I'm struggling with the fact that it won't take over 12 volts like most others do. Being able to plug into a car battery would be a key factor for the "prepper" side of my brain
Can it be modded easily ? I was thinking I could add a second power socket for 13.8 volts but not sure exactly what parts are needed to drop the voltage. I'd like to add a couple of banana plug/screw terminals for easy field use. I'd keep the original power socket for smaller batteries and maybe add a switch to flip between them ?
Love to hear your thoughts. Regards, sean.
Hello,
You could use a 7812 voltage regulator, make a car adapter with it.. Otherwise, three Lithium Ion cells will give you 12.6V max, which works. You put that little 7812 in a little plastic box in your car and you're good to go. You could even put it inside the MTR4b with a switch and add a DC input jack for higher voltages...
Gil.
Thanks Gil, id want something wired internally to run directly off car batteries/battery terminals - im keen to have it all self contained if possible - I might even remove it all from the original box and re-box it with a ZM-2 (or similar) in a single (more solid) case.... and a little active loudpspeaker and a switchable keyer.....along the lines of those project boxes youve been using lately. Then I get options for resonant antennas, random wires and much more.
THe lithium Ion batteries - are they the 18650 you have been using..... that was the plan for portable generally and the screw terminals for "emergency" power when required.
With an adjustable 7812 regulator I suppose I can adjust the transmit power as well.
If you simple need a voltage drop (not a current drop!) a couple of garden variety diodes usually give you a 0.9 volt drop per diode. So, your 13.7ish can RUNNING can have diodes in the power line to drop it below 12 VDC , using your /cigar' lighter/power plug in the car. I have a bunch of 1N400X series power supply diodes I've de-soldered from junk power supplies, which used for this at no cost.
>RadioRay ..._ ._
The 7812 is not adjustable.. I did the diode thing once but the drop was more like 0.4V 1N4004..
Gil
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You need a voltage regulator or a step down.
Example:
https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.com%2Fulk%2Fitm%2F162867196965
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Quote from: Jon_Garfio on May 22, 2018, 05:12:02 AM
You need a voltage regulator or a step down.
Example:
https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.com%2Fulk%2Fitm%2F162867196965
Enviado desde mi Redmi Note 4 mediante Tapatalk
And some ferrit cores wound before it enters the radio I guess. Somewhere I read about extreme noise created from those regulators.
I remember 78xx needs almost 2v above the output voltaje to works fine, If you want 12v and use a 7812, the component needs almost 14vcc.
It is interesting. Tell to me, please - where I can read about it?
Correct Jon, I forgot about that... I am sure there are much better options today, but my electronics schooling dates back to 1985!
Gil.